Document FR-A-2 682 332 describes such a slideway for a vehicle seat which includes a seat back mounted on the seat proper, which back is suitable for tilting down forwards, that slideway comprising:
a "stationary" first rail designed to be secured to the vehicle; PA1 a "moving" second rail designed to support the seat proper, said moving rail being disposed parallel to the stationary rail and being mounted to slide along said stationary rail in a "longitudinal" direction; PA1 a latch mounted on the moving rail, said latch being movable between firstly a locked position in which it co-operates with the stationary rail to prevent the two rails moving relative to each other, and secondly an unlocked position in which it co-operates with the stationary rail and enables the moving rail to slide relative to the stationary rail; PA1 a latch spring urging the latch towards its locked position; PA1 means for manually displacing the latch from its locked position to its unlocked position; PA1 an unlocking lever pivotally mounted on the moving rail to move between two angular positions, firstly an active position in which said unlocking lever acts on the latch holding it in its unlocked position, and secondly a rest position in which said unlocking lever does not act on the latch; PA1 means for moving the unlocking lever from its rest position to its active position, said means being designed to be actuated by the seat back being tilted down forwards; PA1 a lever spring for urging the unlocking lever towards its rest position; and PA1 at least one first abutment member secured in permanent manner to the stationary rail and causing the unlocking lever to return to its rest position when the moving rail is in a predetermined position relative to the stationary rail and when the means for moving the lever are not actuated. The slideway unlocking lever disclosed in that document has a neutral angular position between its active position and its rest position, such that the lever is urged by the lever spring either towards its active position when it lies in an angular position between its neutral and active positions, or else towards its rest position when it is in an angular position between its neutral and rest positions. Thus, when the seat is moved backwards with the unlocking lever in the active position, after the seat has been moved as far forwards as possible, the unlocking lever comes into contact with the first abutment member, thereby causing said lever to pivot progressively from its active position to just beyond its neutral position, while the moving rail continues to move backwards a little. PA1 for the stroke of the latch between its locked position and its unlocked position; PA1 for the shape of the unlocking lever; and PA1 more generally, for the position given to the latch so long as the unlocking lever is between its active position and its neutral position. PA1 the unlocking lever and the trigger are pivotally mounted about two respective horizontal axes perpendicular to the longitudinal direction, the trigger comprising a vertical rigid plate having a top edge extending away from the pivot axis of said trigger to a substantially vertical stop edge, the unlocking lever having a bearing member which, when said unlocking lever goes from its rest position to its active position, presses on the top edge of said plate, moving the trigger from its blocking position towards its retracted position, and then goes past the stop edge of the plate, thus enabling the trigger to return towards its blocking position, said stop edge then co-operating with the bearing member to prevent the unlocking lever from returning towards its rest position; PA1 the stationary rail has a web designed to face downwards, the first abutment member being fixed to the underside of said web; and PA1 the moving rail is longitudinally displaceable relative to the stationary rail between a front abutment position and a back abutment position, the slideway including, in addition to the first abutment member, a second abutment member which is disposed to come into contact with the actuator finger of the trigger when the moving rail is in its back abutment position, then moving said trigger towards its retracted position by a camming effect. PA1 the means for moving the unlocking lever from its rest position to its active position comprise a cable connecting the unlocking lever to the seat back, said cable being mounted to be subjected to traction when the seat back is tilted down forwards, then holding the lever in its active position so long as the seat back is tilted down; PA1 a second slideway extends parallel to the first slideway and has a stationary rail substantially identical to the stationary rail of the first slideway, a moving rail substantially identical to the moving rail of the second slideway, and a latch substantially identical to the latch of the first slideway, the latches of the first and second slideways being mounted to pivot vertically on their respective moving rails between their locked and unlocked positions, each of the latches being disposed on one side of the corresponding slideway in an intermediate space situated between the two slideways, and the two latches being connected to each other by a transverse rigid link bar which is itself secured to an actuator handle and which constrains both latches to occupy identical angular positions; and PA1 the link bar is substantially rectilinear.
When the unlocking lever has gone past its neutral position, it is driven immediately into its rest position by the lever spring, such that the latch can then return to its locked position, thus preventing the seat proper from moving.
The slideway described in the above-mentioned document gives complete satisfaction.
Nevertheless, it requires design decisions that can be awkward and difficult to make:
In that known slideway, those parameters must necessarily be selected so that the latch does not co-operate with the stationary rail of the slideway so long as the unlocking lever is situated in an angular position lying between its active position and its neutral position, otherwise the slideway will jam without locking completely.